162 The Mastigophora 



ever, red haematochrome may accumulate in the cytoplasm in large 

 amounts, as in Euglena rubra (125). Pyrenoids are usually attached to 

 chromatophores or to non-pigmented "pyrenophores" (34). A typical 

 pyrenoid consists of two pyrenosomes, each covered with a paramylum 

 shell and applied to a surface of the chromatophore (Fig. 1. 17, L). The 

 inner pyrenosome may be reduced in size, and is lacking in some cases 

 (34). In such types as Euglena gracilis (Fig. 4. 34, A), there are many 

 chromatophores, each of which probably bears a pyrenoid. At the other 

 extreme, represented by Euglena archaeoplastidiata (Fig. 4. 33, E), there 

 is one chromatophore equipped with two pyrenoids (34). Bleaching of 

 the chromatophores in Euglena gracilis apparently is accompanied by 

 resorption of the pyrenoids, which reappear if the flagellates are returned 

 to the light and develop chlorophyll (240). A stigma, lying on the wall 

 of the reservoir near the paraflagellar body (Fig. 4. 33, A-C), is charac- 

 teristic of green species and also of certain colorless types (120, 237, 240). 

 The stigma may divide in fission (8), or may undergo dispersal and re- 

 aggregation of the piginent granules (96). Flagellar number and struc- 

 ture vary. The bifurcated flagellum of Phacus (Fig. 4. 34, H) and Euglena 

 has been interpreted as a biflagellate condition (Fig. 4. 33, A) in which 

 a rudimentary flagellum is often fused distally with a normal flagellum 

 (110). The bifurcation apparently is absent in Colacium (123) and 

 Rhabdomo7ias (99) but present in Menoidium (240). The situation in 

 Astasia has been disputed, some workers reporting a non-bifurcated and 

 others a bifurcated flagellum. More recent observations (240) indicate 

 that the flagellum, in at least certain species of Astasia, is much like that 

 of Euglena and that the rudimentary flagellum may or may not be in- 

 dependent of the normal flagellum. Such observations support the view 

 that a biflagellate condition is the primitive one and indicate the desir- 

 ability of reexamining those species in which a simple flagellum has been 

 reported. No "bifurcation" has been reported in biflagellate or triflagel- 

 late species. A paraflagellar body (photoreceptor, or flagellar swelling) is 

 characteristic of green species (Fig. 4. 33, A-C) but is absent in colorless 

 forms. 



Stored reserves include lipids and paramylum; the latter is an iodine- 

 negative polysaccharide, insoluble in hot water and yielding glucose on 

 hydrolysis. Paramylum is deposited as refractile bodies which may show 

 concentric stratification in dilute solutions of KOH (62). Size and form 

 may be fairly constant for a species, while the number ranges from typi- 

 cally one (Phacus longicauda) or two {Euglena spirogyra) large bodies to 

 many small ones. 



The life-cycle may include a flagellate stage, a palmella (Fig. 4. 33, M), 

 and a cyst. Fission may occur in both palmella and flagellate stages. 

 Palmella stages are unknown in many species and their distribution 

 within the order remains uncertain, although they may be absent in 



